lecture four - myoglobin and hemoglobin

what is the purpose of myoglobin and hemoglobin

they help direct oxygen to where it is needed

what does the word myoglobin mean

muscle protein

what does the word hemoglobin mean

blood protein

what is the purpose of a heme

it allows the protein to bind to oxygen

how many oxygen molecules can myoglobin bind to

myoglobin is a monomor with one heme so it can bind to one oxygen molecule

when a protein is by itself which form is it in

its apo form

when a protein has its cofactor what form is it in

holo form (whole)

what is the structure of hemoglobin

its an alpha 2 beta 2 tetrameric assembly of monomers this means Hb has four subunits

how many oxygen molecules can hemoglobin bind to

Hb has four subunits each one has a heme that can bind to one oxygen so Hb can bind to 4 oxygen molecules

what state is myoglobin always in

the R-state

what type of curve does myoglobin have

a hyperbolic curve

what is affinity

the ability to bind and the smaller number means there is tighter bonding

what type of oxygen binding curve does hemoglobin have

a sigmoidal curve

what is Hb affinity for O2 at a low PO2 and high PO2

at a lower PO2 Hb has a low O2 affinity its in its T-state, at a high PO2 Hb has a high O2 affinity its in its R-state

what is T-state

if there is an absence of oxygen then the protein is in its tense state in this state the protein has a low affinity for O2

what is R-state

this is the relaxed state which has a high affinity for O2

what is the Bohr effect

this describes how changes in pH and carbon dioxide concentration influence the oxygen binding affinity of hemoglobin

what are the key principles of the Bohr effect

low pH, high CO2 = Hemoglobin releases O2 (T-state favored, in tissues)

high pH, low CO2 = Hemoglobin binds O2 (R-state favored, in lungs)

what does BPG do

binds and stabilizes the Hb T state, at lower PO2 in tissues Hb will release more oxygen than it would if no BPG were present.